1. Field of the Invention
The present invention relates to a light emitting element, and more specifically to a light emitting element in which a solder bonding an LED chip to a substrate is prevented from being squeezed out from the mounting area of the LED chip so that the luminous efficiency of the light emitting element is prevented from being lowered by the squeezed-out solder.
2. Description of the Related Art
A light emitting element including a substrate and a flip-type LED chip flip-bonded to the substrate is known. The flip-type LED chip of the light emitting element includes a first electrode pad connected to a first conductive semiconductor layer and a second electrode pad connected to a second conductive semiconductor layer. The substrate of the light emitting element includes a first lead electrode electrically connected to the first electrode pad and a second lead electrode electrically connected to the second electrode pad. A solder material is used to connect the first and second electrode pads to the first and second lead electrodes, respectively. The electrode pads are connected to the corresponding electrodes by reflow soldering to mount the flip-chip LED chip on the substrate. For uniform distribution of the solder, the solder is applied to an area equal to or greater than the bottom area of the LED chip (i.e. the mounting area of the LED chip) on the substrate. Thereafter, the LED chip is placed on the substrate, followed by reflow soldering.
However, the solder covers the lateral sides of the LED chip and absorbs light emitted from the LED chip, with the result that the about 3% to about 4% of the light is lost. Further, flux remaining in the light emitting element tends to discolor, resulting in an unwanted change in color coordinates. Moreover, non-uniform heat applied to the solder during reflow soldering causes a difference in the degree of melting, resulting in the formation of voids that deteriorate the electrical conductivity and reliability of the solder. The fabrication of the light emitting element requires an additional process for inspecting bonding defects through sporadic sampling. The inspection of bonding defects is also inaccurate.